Field of Invention
The present invention relates to an exhaust gas recirculation valve for a vehicle, and more particularly, to an exhaust gas recirculation valve for a vehicle, capable of improving durability of the valve.
Description of Related Art
In general, a nitrogen oxide (NOx) is noxious gas that is produced by combining oxygen and nitrogen at a high pressure and temperature. In order to suppress the production of NOx, an exhaust gas recirculation (EGR) system is used to lower a maximum combustion temperature by supplying a part of exhaust gas discharged to the atmosphere back to an intake system, and reduce the production of NOx by reducing supply of oxygen.
In the EGR system, an amount of a part of exhaust gas, which is discharged to the atmosphere but supplied back to the intake system, influences a combustion state of fuel, and affects output of an engine, NOx contained in the exhaust gas, particulate matters (PM), and the like.
That is, the EGR system lowers a combustion temperature of the engine and reduces the production of NOx by recirculating a part of exhaust gas discharged from the engine back to an intake device of a cylinder.
As described above, an amount of exhaust gas, which returns, is important in the EGR system, and an EGR valve controls the returning exhaust gas.
Further, in order to control the recirculation of exhaust gas, a flap valve is installed in a recirculation flow path, and an opening degree of the flap valve is controlled by using a driving unit and a lever connected to the driving unit.
However, as a temperature of the recirculating exhaust gas is high, and opening and closing operations of the flap valve are repeatedly performed in accordance with operational states of the engine, repeated stresses are concentrated on components including the flap valve and the lever, and as a result, durability of the components may deteriorate.
That is, as illustrated in FIG. 1, in a case of a general EGR valve, there is a problem in that as a flap valve 12 is shifted in an upper direction due to abrasion of a contact surface between the flap valve 12 and a bushing 11, a portion A where the flap valve 12 and a housing 13 come into contact with each other is abraded.
Further, there is a problem in that the operation of the flap valve 12 fails because the flap valve 12 is trapped in the housing at the time of applying heat.
If stainless steel (SUS) is used as a material in order to solve the above-mentioned problem, hardness rapidly deteriorates at about 550° C. or more, and therefore it is disadvantageous when considering abrasion resistance. In addition, there is a problem in that it is difficult to manufacture the flap valve 12 and the bushing 11 with the same material when considering castability and weldability in terms of a manufacturing method.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.